System and method for mixing and guiding light emitted from light emitting diodes to a light pipe for emission in a linear configuration

ABSTRACT

A linear light module having an optical coupling element and a light pipe is described. The optical coupling element receives light emitted by multiple light emitting diodes (LEDs) having different emission wavelengths and couples the light efficiently to a linear light pipe. The light from the LEDs is efficiently mixed by the optical coupling element and the light pipe to produce a linear light output that is uniform in color and intensity. Diffusers can be used with the optical coupling element and light pipe at various locations to further enhance the uniformity of the emitted light.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the following applications whichare incorporated by reference in their entireties, U.S. ProvisionalApplication No. 61/737,776, entitled “SYSTEM AND METHOD FOR MIXING ANDGUIDING LIGHT EMITTED FROM LIGHT EMITTING DIODES TO A LIGHT PIPE FOREMISSION IN A LINEAR CONFIGURATION,” filed Dec. 15, 2012; U.S.Provisional Application No. 61/737,777, entitled “THERMAL PATH FOR HEATDISSIPATION IN A LINEAR LIGHT MODULE,” filed Dec. 15, 2012; U.S.Provisional Application No. 61/737,779, entitled “MECHANICAL ATTACHMENTSYSTEM FOR LINEAR LIGHT MODULES,” filed Dec. 15, 2012; and U.S.Provisional Application No. 61/737,780, entitled “SYSTEM AND METHOD FORCOMMUNICATION AMONG LINEAR LIGHT MODULES IN A LIGHTING SYSTEM,” filedDec. 15, 2012.

BACKGROUND

Conventional systems for controlling lighting in homes and otherbuildings suffer from many drawbacks. One such drawback is that thesesystems rely on conventional lighting technologies, such as incandescentbulbs and fluorescent bulbs. Such light sources are limited in manyrespects. For example, such light sources typically do not offer longlife or high energy efficiency. Further, such light sources offer only alimited selection of colors, and the color or light output of such lightsources typically changes or degrades over time as the bulb ages. Insystems that do not rely on conventional lighting technologies, such assystems that rely on light emitting diodes (“LEDs”), long system livesare possible and high energy efficiency can be achieved. However, insuch systems issues with color quality can still exist.

A light source can be characterized by its color temperature and by itscolor rendering index (“CRI”). The color temperature of a light sourceis the temperature at which the color of light emitted from a heatedblack-body radiator is matched by the color of the light source. For alight source which does not substantially emulate a black body radiator,such as a fluorescent bulb or an LED, the correlated color temperature(“CCT”) of the light source is the temperature at which the color oflight emitted from a heated black-body radiator is approximated by thecolor of the light source. The CRI of a light source is a measure of theability of a light source to reproduce the colors of various objectsfaithfully in comparison with an ideal or natural light source. The CCTand CRI of LED light sources is typically difficult to tune and adjust.Further difficulty arises when trying to maintain an acceptable CRIwhile varying the CCT of an LED light source and while dimming theintensity level of the LED light source from full intensity to an offcondition when no light is emitted at all.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D depict an example optical coupling element for couplinglight emitted from a light emitting diode (LED) array.

FIG. 2 depicts an example light pipe coupled to an optical couplingelement.

FIGS. 3A-3F depict different views of another example light pipe.

FIGS. 4A-4B depict different views of another example light pipe.

FIG. 5 is a diagram of example components that drive a linear lightmodule.

FIG. 6 shows an end view of an example housing of a linear light module.

FIGS. 7A-7B show views of the ends of an example linear light module.

FIG. 8 shows an example of a linear light module.

FIG. 9 shows a diagram of an example system that includes four linearlight modules.

FIGS. 10A-10H depict different views of another example light pipecoupled to an optical coupling element.

FIG. 11 depicts another example light pipe coupled to an opticalcoupling element.

FIGS. 12A-12C depict example placements of different color LEDs in anLED array.

FIG. 13A shows the placement of different color LEDs in an LED arraythat eliminates the banding effect, and FIG. 13B shows the relativelocations of the LEDs in the array on a CIE color diagram.

FIG. 14 is a diagram of example components of two linear light modulescoupled together.

FIG. 15 shows the relative angles of the emitted rays from two coupledlinear light modules.

FIG. 16 illustrates an example block diagram of a master PCBA 1602coupled with a slave PCBA 1604.

FIG. 17 is a flow diagram illustrating an example process of creating apatterned diffuser.

FIG. 18 is a flow diagram illustrating another example process ofcreating a diffuser.

FIG. 19 is a flow diagram illustrating an example process of removingheat from a linear light module.

FIG. 20 is a flow diagram illustrating an example process of holding alight pipe in place relative to a housing when the light pipe and thehousing have different thermal coefficients.

FIG. 21 is a flow diagram illustrating an example process of determiningrelative placement locations for different color LEDs in an LED array.

DETAILED DESCRIPTION

A linear light module that provides a uniform distribution of tunableillumination along the length of the light module is described. Two ormore light modules can be used together to provide a seamless longerlinear source of illumination. In some embodiments, when multiple lightmodules are used together in a system, one of the light modules isdesignated as the primary module which can function as a primaryreceiver of light tuning commands, and the primary module re-transmitsthe commands to other modules of the system.

Various aspects and examples of the invention will now be described. Thefollowing description provides specific details for a thoroughunderstanding and enabling description of these examples. One skilled inthe art will understand, however, that the invention may be practicedwithout many of these details. Additionally, some well-known structuresor functions may not be shown or described in detail, so as to avoidunnecessarily obscuring the relevant description.

The terminology used in the description presented below is intended tobe interpreted in its broadest reasonable manner, even though it isbeing used in conjunction with a detailed description of certainspecific examples of the technology. Certain terms may even beemphasized below; however, any terminology intended to be interpreted inany restricted manner will be overtly and specifically defined as suchin this Detailed Description section.

The correlated color temperature (CCT) of light generated by a lamp istunable by adjusting the amount of light contributed by distinct sourceswithin the lamp that generate different wavelengths of light. Forexample, the amount of current supplied to multiple light-emittingdiodes (LEDs) that emit light having different peak wavelengths can beadjusted to change the CCT of the light generated by the lamp. Examplealgorithms for tuning the light emitted by multiple LEDs to a specificCCT is described in more detail in U.S. patent application Ser. No.13/766,695 entitled, “System and Method for Color Tuning Light Outputfrom an LED-Based Lamp” and is incorporated herein in its entirety. Thelight emitted by the individual LEDs should be well mixed so that thereare no visible hot spots of individual colors, particularly if theillumination surface of the lamp is extended, as with the linear lightmodules.

FIG. 8 shows an example linear light module that can be used as amodular building block for a lighting system. In some embodiments, thelinear light module is designed to be a particular standard length, e.g.one-foot or two-foot long lengths, similar to conventional lightinglengths. However, the linear light module can be designed to have anydesired length. A visually appealing light is characterized by a uniformillumination intensity along the entire length of the lighting unitwithout perceptible hot spots or color spots. To accomplish this, thelight emitted from the multiple LED sources in the lamp should beefficiently coupled and mixed to provide the uniform illumination as itis directed to the portion of the light module that is visible to users(the white bar in the upper middle of the unit shown in FIG. 8). At thesame time, to make the linear light module efficient, the design of themodule should prevent light from leaking out of the light module beforeit reaches the intended emission surface.

Optical Coupling Element and Linear Light Pipe

An initial optical coupling element 100 is used to efficiently couplethe light emitted by the LEDs. In some embodiments, another type oflight source can be used, such as a fluorescent light source or halogenlight source. The optical coupling element 100 can be made from anymaterial that transmits the wavelengths of light generated by the LEDsources, for example, optical grade acrylic. One example of the opticalcoupling element is shown in FIGS. 1A-1D. The input surface 110 of theoptical coupling element 100 has multiple concave inward cavities. Insome embodiments, as shown in FIG. 1A, the input surface 110 has a pairof troughs 112, 114, with each trough sufficiently wide to receive thelight emitting surface of a single LED and sufficiently long to receivethe light emitting surfaces of multiple LEDs, for example, multiple LEDsarranged in an array. A cross-section of the troughs 112, 114 are shownin FIG. 1D. The troughs are filled with a coupling material, such assilicone gel, to couple the LEDs to the optical coupling element 100.The configuration of concave inward cavities is not limited to twoparallel troughs, rather any number of troughs in any convenient layoutfor one or more LED arrays can be used. In some embodiments (not shown),the input surface 110 can have a dedicated concave cavity for eachindividual LED in the light source.

The optical coupling element 100 is designed to couple light from theLEDs through the input surface 110 and emit the coupled light through anoutput surface 140, where the output surface 140 is opposite the inputsurface 110. In some embodiments, the optical coupling element 100 issymmetrical along the two substantially perpendicular midlines of theinput surface 110 or the output surface 140. The input surface 110 andoutput surface 140 are coupled by several side surfaces of the opticalcoupling element 100, namely surfaces 130, 131, 120, 121, and thesurfaces on the opposite sides of the optical coupling element 100 tothese surfaces. These side surfaces are designed to use total internalreflection (TIR) to reflect most of the light from the LEDs within theoptical coupling element 100 until the light exits the optical couplingelement 100 from output surface 140. For example, light that enters theoptical coupling element 100 through input surface 110 can strike afirst surface 130 at greater than the critical angle, be totallyinternally reflected to strike a second surface opposite the firstsurface at greater than the critical angle to again be totallyinternally reflected, and exit the output surface 140.

Light rays that strike the surfaces of the optical coupling element 100at less than the critical angle will be transmitted out of the opticalcoupling element 100. Thus, the curvatures of the side surfaces of theoptical coupling element 100 are designed to ensure that most of thelight from the LEDs strike the side surfaces at greater than thecritical angle. In some embodiments, the surfaces 130, 131, 120, 121,and their opposing surfaces of the optical coupling element 100 areparaboloids.

Further, to maximize the coupling efficiency of the optical couplingelement 100, a reflective surface, such as Miro silver, can bepositioned behind each surface 130, 131, 120, 121, and their opposingsurfaces to reflect escaping light back into the optical couplingelement 100. The reflective surface is separated from the opticalcoupling element 100 by a small air gap to ensure that conditions fortotal internal reflection (TIR) are met for angles greater than thecritical angle, i.e., the index of refraction of the optical couplingelement 100 is greater than the material immediately on the outside ofthe optical coupling element 100. If the reflective surface is applieddirectly to the surfaces of the optical coupling element 100, the TIRmechanism would not be effective, rather all the light striking thesurface of the optical coupling element 100 would exit the opticalcoupling element 100 and be directly reflected from the reflectivesurfaces, resulting in a lossier reflection mechanism. The reflectivesurfaces in conjunction with the TIR mechanism of the optical couplingelement 100 ensure that the amount of light lost between the inputsurface 110 and the output surface 140 of the optical coupling element100 is very low. However, in some embodiments, as described below, itmay be beneficial to not use the reflective surface behind one or moresurfaces of the optical coupling element to allow light to escape fromselect surfaces into a light pipe.

In some embodiments, there are two criteria that the light exitingoutput surface 140 of the optical coupling element 100 should meet. Thefirst criterion specifies a range of exit angles of the light from theoutput surface 140, such that light satisfying the specified range ofexit angles will continue to be reflected via TIR within a light pipecoupled to the output surface 140. Thus, the shape of the light pipe cancontribute to the desired range of exit angles. FIG. 2 shows an opticalcoupling element 210 with an exit surface 212 coupled to an examplelight pipe 220. The bottom surface 227 of the light pipe 220 issubstantially normal to the output surface 212 of the optical couplingelement 210, and the top surface 221 (the emitting surface) of the lightpipe 220 is substantially parallel to the bottom surface 227. Althoughthe light pipe emission surface 221 is above the height of the opticalcoupling element 210, the shape of the light pipe 220 is substantially arectangular solid. The light pipe has an elongated shape to ensure thatthe light is eventually emitted in the desired linear configuration.Further, the length of the light pipe can be used advantageously to mixthe light before being emitted, as described below.

For the example light pipe 310 shown in FIG. 3A, the bottom surface 314of the light pipe 310 is tapered upward toward the emission surface 312,and the top emission surface 312 is still substantially perpendicular tothe surface 315 where the output surface 140 of the optical couplingelement 100 would couple to the light pipe 310.

The example light pipe 410 shown in FIG. 4A is similar in shape to thelight pipe 310, but the bottom surface 414 is stepped, rather having asmooth taper, and the bottom surface 414 rises toward the emissionsurface 412. For ease of reference, surfaces herein may be referred toas the bottom surface and the top surface, corresponding to theorientation of the element shown in the figures. However, the elementcan have any orientation, and the bottom surface does not have to facedownward, nor does the top surface have to face upward.

The second criterion specifies an exit aperture so that most of theexiting light will be contained within certain dimensions of the outputsurface 140. Essentially the rays of light emitted from the extreme edgeof the LED array that cross the optical coupling element 100 will havethe least steep angle. The angle at which these rays strike the opticalcoupling element 100 must be greater than the critical angle in orderfor these light rays to undergo TIR. Thus, these light rays willdetermine the geometry of the optical coupling element 100, and anadditional margin on the angle of these rays can also be taken intoaccount when designing the optical coupling element 100. The secondcriterion works in conjunction with the first criterion to ensure thatmost of the light exiting the optical coupling element 100 will bereflected within the light pipe through the mechanism of TIR until thelight strikes the desired emission surface of the light pipe.

FIG. 2 illustrates one example configuration where the optical couplingelement 210 is coupled to a light pipe 220. Similar to the opticalcoupling element 100, the light pipe 220 can be made from any materialthat transmits the wavelengths of light generated by the LED sources,such as optical grade acrylic. The output surface 212 of the opticalcoupling element 210 is coupled to a side surface of the light pipe 220using an optical coupling material, such as silicone or coupling gel.

In some embodiments, the top surface 221 of the light pipe 220 is thesurface from which the light is emitted by the lighting module, forexample, as shown by the white strip of the light module in FIG. 8.Similar to the side surfaces of the optical coupling element 100, threeside surfaces of the light pipe are backed by a reflective surfaceseparated from the light pipe by an air gap: the surface 222 as seen inFIG. 2, the surface 227 that is opposite surface 221 (on the bottom ofthe light pipe as depicted in FIG. 2), and the surface opposite thesurface 222. These surfaces are separated from the reflective surface byan air gap so that the TIR mechanism functions to keep most of the lightwithin the light pipe, and only the small percentage of light thatstrikes the surface of the light pipe 220 at an angle less than thecritical angle leaks out of the light pipe, to be reflected back intothe light pipe by the reflective surface.

The light pipe 220 has a distal surface 225 and an opposing end surface226 near the optical coupling element 210. The distal surface 225 of thelight pipe 220 can be placed immediately next to the opposing endsurface 226 of a second light pipe to produce a longer light emittingsurface. FIG. 9 shows four linear light modules 910, 920, 930, 940placed immediately adjacent to each other such that the light emittingsurfaces of the four modules form a continuous linear surface with noperceptible joint between the light pipes. A system having multiplelight modules will be described below.

When a linear light module is used independently of other linear lightmodules, both the distal surface 225 and the opposing end surface 226should be covered with reflective caps to prevent light from propagatingout the ends of the light pipe 220. Light that is reflected from the endcaps back into the light pipe 220 bounces within the light pipe untilthe light exits the desired emission surface 221.

Because the light coupled from the LED sources by the optical couplingelement 100 enters the light pipe 220 from the optical coupling element210 from a surface 212 that is oriented in a direction substantiallyperpendicular to the emission surface 221, rather than in a directiontoward the emission surface 221 of the light pipe 220, there is a strongaxial component to the light rays. The optical coupling element 100 isdesigned so that the rays entering the light pipe will strike thesurface of the light pipe 220 at an angle greater than the criticalangle so that the light will undergo TIR instead of exiting a surface ofthe light pipe 220. Because the light pipe 220 in FIG. 2 is arectangular solid, the light rays will spiral down the light pipe and bereflected to spiral back in the direction of the light source. It wouldbe advantageous to mix the light while it is traveling down the lightpipe so that light from the individual LEDs becomes well mixed to reduceintensity and color hot spots.

One way to mix the light in the light pipe is make the surface oppositethe emission surface of the light pipe 220 a rippled surface. Forexample, small amplitude grooves or ribs can be extruded or molded intothe side surfaces of the light pipe. Then the light rays will stillundergo TIR reflection at those surfaces of the light pipe, but the rayswill no longer reflect in a repeating prismatic pattern. Rather, therays will be scattered in different directions as they hit the rippledsurface and develop a stronger peripheral component and a weaker axialcomponent. In some embodiments, the other surfaces of the light pipe canalso be made with a rippled surface.

FIGS. 3A-3F show an example configuration of a light pipe 310 that has atapered bottom surface 314. FIG. 3A shows a side view of the light pipe310, and FIG. 3F shows a perspective view of the light pipe 310. Due tothe taper of the bottom surface, the angle that a light ray strikes eachsurface of the light pipe with respect to a surface normal becomessteeper and steeper until the conditions for TIR no longer hold, and thelight exits the light pipe. Typically, the light exits the light pipe atan angle near the critical angle so that there is still a strong axialcomponent to the light. Consequently, the intensity of the emitted lightdoes not appear uniform in all directions. To remedy this situation, adiffuser (described below) can be used on the emission surface, thesurface of the light pipe opposite the exiting surface, or both.

FIGS. 4A-4B show an example configuration of a light pipe 410 that has astepped bottom surface. The step formation of the bottom surface helpsto mix the light within the light pipe so that the emitted light is moreuniform.

FIGS. 10A-10H show different views of yet another configuration of alight pipe 1010 that has a primarily concave upwards shape along most ofthe bottom surface 1020 (opposite the emission surface 1030) with a flatportion near the end of the light pipe 1010 with the optical couplingelement 1050. Additionally, the bottom surface 1020 has saw-tooth likefeatures. In some embodiments, the amplitude of the features can varyalong the length of the bottom surface 1020. For example, as shown inFIG. 10A the amplitude of the features is largest near point J along thelength of the bottom surface 1020 and is constant until point K. Thenfrom point K to point L, the amplitude monotonically decreases. In someembodiments, the amplitude of the features can increase or decreasealong the length of the bottom surface and can even be random. In someembodiments, the amplitude of the saw-tooth features can be selected tobe easily machinable, for example, on the order of a millimeter orgreater.

The function of the saw-tooth features is to extract light from thelight pipe 1010 to further mix the light from the optical couplingelement 1050. As described above, the surfaces of the light pipe 1010,except for the emission surface 1030 are backed by a reflective surfaceseparated from the light pipe 1010 by an air gap. Light extracted fromthe light pipe by the saw-tooth features is reflected back into thelight pipe 1010 through the saw-tooth features into the light pipe 1010again, causing the light to be mixed.

In some embodiments, finer features on the order of tens of microns tohundreds of microns in amplitude can be used. These finer features canbe saw-tooth or convex or concave features, such as dots or bars. Thefiner features can be periodic, aperiodic, clusters, and/or varying indensity. Further, the finer features can be machined or molded as partof the light pipe. Because the function of the features is to extractlight from the light pipe, with finer features, there is more controlover the uniformity of the light that is emitted by the light pipe.

Further, there is a portion of the light pipe that is above the opticalcoupling element 1050 and cantilevered out beyond the optical couplingelement 1050 on the left, referred to as a bridge 1040. In thisembodiment, the side surfaces of the optical coupling element 1050 arebacked by a reflective surface separated from the optical couplingelement 150 by an air gap, except for portions of or all of the topsurface. Instead, at the top surface, the optical coupling element 1050physically contacts the bridge 1040, thus removing the condition for TIRinside the optical coupling element 1050 and causing some of the lightin the optical coupling element 1050 to leak into the bridge 1040. Atleast at the portions where the optical coupling element 1050 and thebridge make contact, there is no reflective surface used. The bridge1040 is used to ensure that the light emitted from emission surface 1020is uniform, primarily in the region above the optical coupling element1050. In some embodiments, the bridge 1040 is separate from the rest ofthe light pipe 1010, and is physically attached to the top of theoptical coupling element 1050.

To send even more light to the bridge 1040, there is a slot 1060 angledaway from the bridge 1040 next to a middle section 1070 within the lightpipe 1010. Light exiting the top surface the optical coupling element1050, where there is no reflective surface backing, will enter the slotand be reflected to the left toward the bridge 1040. The angled sides ofthe middle section 1070 further reflect the light toward the emissionsurface 1030.

FIG. 11 shows yet another configuration of a light pipe 1110 that has aconcave upward shape with saw-tooth like features along most of thebottom surface 1120 opposite the emission surface 1130, similar to thelight pipe 1010 shown in FIG. 10A. However, the bridge 1140 and lightpipe 1110 in the example configuration shown in FIG. 11 are molded as asingle piece with an air gap between the optical coupling element 1150and the bridge 1140. The width of the air gap can be variable orconstant. In some embodiments, the width of the air gap can be betweenapproximately 2 mm and 6 mm. The length of the air gap starts from abovethe LED array 1155 and extends to the diffuser in some embodiments, andbeyond the diffuser in other embodiments.

Light is extracted from the optical coupling element 1150 through alight extraction element 1190 coupled to the top surface of the opticalcoupling element 1150 that is facing toward the bridge 1140.Non-limiting examples of the light extraction element 1190 can include abrightness enhancement film, diffusion film, or other type of diffuser.The length and width of the light extraction element 1190 can bedesigned to extract a desired amount of light from the optical couplingelement 1150 for coupling to the bridge 1140.

As shown in FIG. 15, the light emitted from emission surface 1130 by thelight pipe 1110 is angled from the vertical in a plane defined by thelongitudinal axis of the light pipe and the height of the light pipe(i.e., the plane of the paper as shown in FIG. 15). The light is angledfrom vertical because this is the condition for which the condition forTIR is no longer met. In some embodiments, the angle of is approximately30 degrees. As shown in the example light configuration of FIG. 15, twolight pipes can be placed end to end, where the light pipes face inopposite directions. Rays emitted from vertical in a first directionfrom the first light pipe, and rays emitted from vertical in a seconddirection, opposite from the first, from the second light pipe can bedesigned to strike a reflector or a diffuser to make the light appearuniform in the far field to an observer. As a result, the observer willno longer be able to identify that the light coming from each of thelight pipes was originally emitted in different directions.

Diffusers

In some cases, the embodiments of the light pipe depicted in FIGS. 2-4as well as other embodiments of a linear light guiding pipe can providea more uniformly mixed illumination output through the use of a diffuseron the exit surface, for example, exit surface 221 of the light pipe 220in FIG. 2. The diffuser functions by breaking up the light reaching theemission surface at an angle smaller than the critical angle andre-directing portions of that light into different directions. A portionof the light will leave the exit surface after being diffused by thediffuser, while another portion of the light will re-enter the lightpipe to be reflected within the light pipe until it reaches the exitsurface again and is re-diffused by the diffuser on the exit surface.

The diffuser can be just as effective in mixing the light when placed onthe bottom surface of the light pipe opposite the exit surface. However,rather having a portion of the light that strikes the bottom surface atsmaller than the critical angle being diffused by the diffuser andpermanently exiting the light pipe, the light is reflected back into thelight pipe by the reflective surface outside the light pipe. Thisreflected light is diffused again by the diffuser when re-entering thelight pipe. The light will be reflected within the light pipe, either byTIR or by being directly reflected by a reflective surface outside ofthe light pipe, eventually being emitted from the exit surface of thelight pipe.

The use of the diffuser on either the exiting surface or the oppositesurface of the light pipe helps to mix the light from the different LEDsources inside the light pipe to produce a more uniform illumination atthe exit surface of the light pipe. Without the use of a diffuser, therecan be gradients in the intensity of the light within the light pipe.For example, the intensity of the light seen from one end of the lightpipe, for example, looking into end face 225 of the light pipe 220 inFIG. 2 can be stronger than the intensity of the light seen looking intothe opposite end face 226 of the light pipe 220.

Various materials can be used on the emission surface and/or theopposite surface of the light pipe to homogenize the light in the lightpipe, for example, a diffusive material such as a laminated diffusionfilm, a molded textured surface, a diffusive reflector, and/or aspectral reflector. In some embodiments, various combinations of shapesand materials can be used on the emission surface and/or the oppositesurface. For example, the diffusive material need not cover the entireemission surface or the entire opposite surface. The diffusive materialcan be used in one or more discrete sections along the light pipe indifferent patterns, either uniform or non-uniform.

Alternatively or additionally, more than one type of material can beused in different patterns along the emission surface and/or theopposite surface of the light pipe. For example, a diffusive materialcan be alternated with a spectral reflector along the length of thelight pipe.

In some embodiments, a brightness enhancement film, made by, forexample, 3M of Maplewood, Minn. can be used. The brightness enhancementfilm is directional with grooves in the film aligned in a particulardirection. In some embodiments, the brightness enhancement film can bepositioned with the grooves at one or more angles, for example, auniform or non-uniform patchwork of groove angles can be used along theemission surface and/or the opposite surface. The brightness enhancementfilm can be used either alone or with another type of diffusive materialin a uniform or non-uniform pattern.

A separate steering element can be placed over the emission surface ofthe light pipe with an air gap between the steering element and theemission surface to further reduce the axial component of the emittedlight. In some embodiments, the steering element has a saw tooth patternon the surface closest to the light pipe to diffract the light indifferent directions.

The configurations of the light pipe depicted in FIGS. 10A-10H and FIG.11 as well as other embodiments of the linear light pipe can provide amore uniformly mixed illumination output through the use of a diffuser1080, 1180 between the optical coupling element and the light pipe.Further, a diffuser can be used as the light extraction element 1190shown in FIG. 11.

A Patterned Light Diffuser

A diffuser can be the final mixing element for eliminating any remaininghot-spots by diffusing light exiting an optical element, such as a lightpipe, or an optical coupling element that couples light from LEDs, intoa large range of angles to homogenize both the color and intensityvariations at the diffuser exit, thus providing more uniformillumination.

Better mixing is typically achieved by increasing the diffusion angle ofthe diffuser to cause the light impinging on the diffuser to spread overa wider range. As a result, light from the various hot spots on thediffuser interfere with each other and decreases the color and intensitygradients perceptible in the output beam.

However, higher diffusion usually results in higher losses so there is atradeoff between higher diffusion and lower light output. Describedbelow are two manufacturing processes by which better light mixing canbe achieved with lower losses than with conventional manufacturingprocesses. The first process replaces plastic diffusers with coatedglass so that much higher optical flux densities can be diffused withoutdegradation of the plastic with time and temperature.

A patterned diffuser with plain uncoated glass between patternedsections can effectively cause a large amount of light mixing whilestill allowing a significant amount of the light to pass with low lossthrough the glass.

FIG. 17 is a flow diagram illustrating an example process of creating apatterned diffuser. At block 1705, scattering particles, such as Kaolinclay, are milled and screened for particles having a size approximatelyless than or equal to two microns, or any other suitable size.

Then at block 1710, the scattering particles are mixed in a suspensionsolution. In some embodiments, the suspension solution can be a siliconeadhesive, such as made by DuPont of Wilmington, Del.

Next, at block 1715, controlled amounts of the mixture are patternedonto a substrate, such as a glass substrate. In some embodiments, themixture can be squeezed through a pattern of micro-holes to depositdrops onto the glass substrate. The pattern of holes can include holeswith a pre-determined diameter and a predetermined pitch. In someembodiments, the mixture can be made thinner to have a lower viscosity,and the resulting mixture can be deposited onto the glass substrate byspin-coating or spraying. This results in a smooth layer, but theresulting diffuser will not have a pattern.

At block 1720, the glass substrate with the deposited mixture is heated,for example, in an oven, until the adhesive has cured. The result is alight diffuser that can withstand high optical flux densities.

FIG. other is a flow diagram illustrating an example process of creatinga diffuser. As described above, at block 1805, scattering particles,such as Kaolin clay, are milled and screened to produce Kaolin powder.The proper ratio of silicone and scattering particles can beexperimentally determined for the desired diffusive effect.

Then at block 1810, the injection moldable silicone is compounded withthe scattering particles to produce a resin premix. At block 1815, theresin premix can be injection molded to produce diffusers in variousdesired shapes.

LED Array

The LED array used with the optical coupling element can have any numberof LEDs, for example, a 2×5 LED array can be used. The wavelengths oflight emitted by the LEDs in the array are selected so that the combinedlight from all the LEDs generate a desired CCT. The array may includeLEDs having different colors and one or more white LEDs. Because themixing of the light from the multiple LEDs achieved from bouncing thelight against the surfaces of the optical coupling element and lightpipe and the outer reflective surfaces before being emitted from theemission surface of the light pipe is not perfect, it would bebeneficial to select the placement of the individual colored LEDs in thearray to ‘pre-mix’ the light to produce a more uniform lightdistribution at the emitting surface of the light pipe withoutdiscernible bands of colors.

In embodiments of the linear light module described above having anoptical coupling element emitting directly into an adjacent light pipe,a horizontal banding effect may be visible along the emission surface ofthe light pipe. The banding effect arises due to insufficient mixing ofthe light emitted from adjacent LEDs.

FIGS. 12A-12C show three different placements of LEDs in an LED array.The symbol W corresponds to a white color LED; R corresponds to a redcolor LED; A corresponds to an amber color LED; G corresponds to a greencolor LED; and B corresponds to a blue color LED. FIG. 12A shows a 2×5LED array where the top three rows of LEDs do not additively combine toproduce light that is nearly white. As a result, if there isinsufficient mixing of the light from the array by the optical couplingelement and the light pipe, bands of colored light corresponding to theadditive color of each of the rows of LEDs in the array may be seenperiodically along the emission surface. Thus, the top row of the LEDarray causes periodic red bands of light along the emission surface ofthe light pipe, the second row causes periodic amber bands of light, andthe third row causes periodic bands of greenish-blue light.

One way to eliminate color bands along the emission surface is to selectpairs of LED colors that are nearly opposite each other in chromaticityspace across the Planckian locus to be placed adjacent to each other.FIG. 13 shows a CIE 1931 chromaticity space diagram with a Planckianlocus, the path that the color of a black body takes as the blackbodytemperature changes. Each LED color in the LED array is represented by adot on the diagram and is labeled with the first letter of the coloremitted by that LED (R for red, A for amber, G for green, B for blue,and W for white). Lines between the dots connect pairs of LED colorsthat when mixed, produce nearly a white color. For example, the redcolor LED (R) is paired with the amber color LED (A); the amber colorLED is paired with the blue color LED; and the red color LED is pairedwith the green color LED. FIGS. 12B and 13A show a 2×5 LED array withthese LED color pairings. The light emitted by a linear light modulethat uses this placement configuration for the LEDs in the LED arraydoes not exhibit discernible color bands across the emission surface.

FIG. 12C shows a 3×3 LED array where each row of three LEDs producenearly a white color. There is a white LED in the center of each row,and the white light is combined with a red color LED and an amber colorLED in the first row, with a green color LED and a red color LED in thesecond row, and with an amber color LED and a blue color LED in thebottom row.

Because it is beneficial to pre-mix the light as much as possible asearly as possible before being emitted from the emission surface of thelight pipe, a diffuser 1180 can be added to the output surface of theoptical coupling element, as shown in the example light pipeconfiguration of FIG. 11. The diffuser 1180 diffuses the light exitingthe optical coupling element 1150 prior to being mixed as it reflectsfrom the surfaces of the light pipe 1110 and the outer reflectivesurfaces.

FIG. 21 is a flow diagram illustrating an example process of determiningrelative placement locations for different color LEDs in an LED array.At block 2105, a number of LEDs and a plurality of emission wavelengthsof the LEDs are initially selected to produce a desired CCT and outputpower. Then at block 2110, each of the corresponding colors for theselected LED emission wavelengths are plotted on a color diagram. Atblock 2115, for each row of LEDs in an LED array, the LEDs are selectedby emission color so that the additive color emitted light of the LEDsin a row generates nearly white light.

Providing a Thermal Path for Heat Generated by the LEDs

FIG. 5 shows example elements in the linear light module 800 thatgenerate the illumination provided by the module. In the example of FIG.5, the light source is a 2×5 LED array. However, any number of LEDs inany configuration can be used as the light source. The LED array iscoupled to the optical coupling element 100 as described above.

The electronics for driving the LED array are included in a printedcircuit board assembly (PCBA) that is coupled to the LED array through aflex circuit. A flex circuit is used to couple the PCBA to the LED arraybecause the flex circuit allows for thermal expansion of elements due toheating by the LEDs without impacting the alignment of the LEDs with theoptical coupling element 100.

Coupled directly to the flex circuit is a heat transfer block made froma thermally conductive material, such as copper. The heat transfer blockconducts the heat generated by the LED array to a heat pipe that ispositioned along the inside of a housing of the light module. In someembodiments, the housing is made from a thermally conductive material,such as aluminum. Thus, there is a thermal path for the heat generatedby the LEDs to the aluminum housing. The mounting for the heat pipe isshown in FIG. 6. The heat pipe is also made from a thermally conductivematerial that transfers heat to the housing. The housing acts as a heatsink and is in contact with the environment to dissipate heat generatedby the LEDs from the light module.

FIG. 19 is a flow diagram illustrating an example process of removingheat from a linear light module. At block 1905, heat is conducted awayfrom the lighting source via a heat transfer block. Then at block 1910,heat is conducted away from the heat transfer block via a heat pipe. Andat block 1915, heat is conducted away from the heat pipe via a housingof the linear light module and the lighting source.

FIG. 5 also shows registration markers that are used to pin the lightpipe and the housing together at a single point, and yet allow them tomove relative to each other due to different thermal coefficients thatresult in different rates of thermal expansion. The housing has ahemispherical bump, and the light pipe has a matching hemisphericalrecess. FIG. 7A shows the back side of the view shown in FIG. 5 with abetter view of the hemispherical recess 722 in the light pipe 720. Forreference, light from the 2×5 LED array 752 is coupled to the flexcircuit 750, and the light from the LEDs is coupled by the opticalcoupling element 710 to the light pipe 720. The heat pipe mounting 730is also shown in the housing 740. In some embodiments, the shape of thematching bump and recess can be different from hemispherical. Thedimensions of the recess in the light pipe is small so that the lightwithin the light pipe is effected a minimal amount, yet large enough toprevent the light pipe from moving.

FIG. 7B shows the distal end of the light pipe 720 and housing 740.Because the light pipe is only pinned to the housing at a singlelocation, the light pipe can expand longitudinally along the length ofthe lighting module (in the z-direction) relative to the housing.Although the light pipe cannot move in the x-direction because it isclamped between the two sides 741, 742 of the housing 740, the lightpipe 720 can also expand in the y-direction between the sides 741, 742of the housing.

By allowing the light pipe the freedom to move relative to the housing,stress due to thermal expansion is relieved to prevent breakage of theLEDs.

FIG. 20 is a flow diagram illustrating an example process of holding alight pipe in place relative to a housing when the light pipe and thehousing have different thermal coefficients. At block 2005, a recessedregistration guide is placed on a light pipe. Then at block 2010, amatching registration bump is placed on a housing for the light pipe anda lighting source.

Next, at block 2015, the light pipe and the housing are allowed tothermally expand at different rates in a first direction along a lengthof the light pipe while maintaining the registration bump within therecessed registration guide. At block 2020, the light pipe and thehousing are allowed to thermally expand at different rates in a seconddirection substantially perpendicular to the first direction whilemaintaining the registration bump within the recessed registrationguide. Finally, at block 2025, the light pipe is clamped in a thirddirection by the housing which limits thermal expansion of the lightpipe in the third direction, wherein the third direction issubstantially perpendicular to the first direction and the seconddirection.

Mechanically Coupling Together Multiple Linear Light Modules

The linear light module 800 shown in FIG. 8 uses a light pipe that hasend faces that are flat and perpendicular to the axis of the light pipe,such as in the example light pipes of FIGS. 2-4. When the linear lightmodule 800 is used as a stand-alone unit, the end faces of the lightpipe, for example, surfaces 225, 226 in FIG. 2 are covered with areflective surface to reflect light exiting these surfaces back into thelight pipe to bounce around until eventually being emitted through theemission surface 221.

In some embodiments, more than one linear light module 800 can becoupled together to form a longer continuous emission surface. FIG. 9shows an example system where four linear light modules 910, 920, 930,940 are coupled together as a system 900. In this case, the light pipeof each of the linear light modules 910, 920, 930, 940 touch, or nearlytouch, each adjacent light pipe to form a single continuous linearemission surface. The example system of FIG. 9 shows three types ofmodules, a primary module 910 on the right of the system, two secondarymodules 920, 930 in the middle of the system, and an end unit 940 on theleft end of the system.

The primary module 910 has a reflective end cap on the end of its lightpipe nearest to the LED sources, corresponding to, for example, surface226 of light pipe 220 in FIG. 2. The opposite end of the light pipe,corresponding to, for example, surface 225 in FIG. 2, is not covered bya reflective material. Thus, light escaping from this surface of thelight pipe of module 910 enters the adjacent light pipe of the nextlight module 920.

For the secondary modules 920, 930, neither end of the light pipe iscovered so that light can be transmitted between the light pipes of thefour modules 910, 920, 930, 940.

For the end module 940, the end of the light pipe farthest from the LEDsources, corresponding to, for example, surface 225 of light pipe 220 inFIG. 2 is covered with a reflective end cap to prevent light fromescaping from this surface. The opposite end of the light pipe closestto module 930 is not covered with reflective material to permit lightfrom the light pipe of module 940 to enter the light pipe of the module930, and to permit light from the light pipe of module 930 to enter thelight pipe of module 940.

A person of skill in the art will appreciate that the length of thelight pipes can be designed to be a single length (e.g. one foot or twofoot long light pipes), different standard lengths (e.g., one foot, twofeet, three feet, etc.), or customized lengths. Thus, the linear lightmodules can be used as modular building blocks for designing a lightingsystem having various lengths FIG. 9 shows four two-foot modules coupledtogether to form a continuous eight foot long light emission surface.Each two-foot module can have a single two-foot long light pipe having asingle LED array, for example a 2×5 array. Alternatively, each two-footmodule can be made up of two one-foot long light pipes where each lightpipe couples light from a separate LED array, for example, two 2×5arrays of LEDs can drive the two-foot module together.

Two linear light modules that each use light pipes that do not have flatend faces, such as the light pipes shown in the examples of FIGS. 10 and11 can be paired together to form a single composite light emissionsurface, as shown in the example configuration of FIG. 15. The lightpipes are placed end to end where the farthest end of the light pipefrom the optical coupling element of a first light pipe is placedclosest to the counterpart end of the second light pipe farthest fromthe optical coupling element. In some embodiments, each light pipebuilding block is approximately one foot long, providing a two-foot longlight when two light pipes are coupled together. Each light pipe has itsown LED array source. Thus, with two light pipes, twice the light isemitted as compared to a single light pipe. The length of the compositelight emission surface can be extended by adding on additional modules,either as a single unit or in pairs as described above.

In one embodiment, the linear light modules are designed to attach froma fixture, a wall, or the ceiling. To permit the light pipe of theadjacent linear light modules to touch, or nearly touch, a mechanicalsystem is used that clips the adjacent linear light modules together. Inone embodiment, the linear light modules should be able to slidedirectly into place from below (in a direction perpendicular to theemission surface) without needing to slide into place horizontallybecause there is no room to slide the modules horizontally.

The linear light modules can be clipped together using the dovetailgrooves in the extruded housing of the modules shown in FIG. 6. In oneembodiment, a clip or other fastener can be used with these grooves tomechanically couple together two adjacent linear light modules.

In one embodiment, the grooves can be used with a rail system so thatthe linear light modules can be attached together using a rail, and auser can use the rail to attach the linear light modules together or toa particular surface, such as a wall or ceiling.

In one embodiment, the side grooves shown in FIG. 6 can be used to cliptogether adjacent light modules. Alternatively or additionally, opticssuch as reflectors can be clipped onto the light module using the sidegrooves. Similarly, the reflector/lens mounting near the emissionsurface of the light pipe can also be used for attaching optics onto themodule.

Communications and Power Transmission Among Coupled Light Modules

Each lighting module has a PCBA that includes the electronics fordriving the LED array, and the PCBA has two connectors. One connector(the near connector) is near the LED array. The other connector (the farconnector) is on the far side of the light module. These connectors canbe used to optionally couple to adjacent light modules so that power andcommunication signals can be sent between light modules.

The system 900 shown in FIG. 9 has four coupled light modules 910, 920,930, 940, and the modules are mechanically coupled as described above.Additionally, each of the modules has a PCBA 911, 921, 931, 941 with twoconnectors that can be used to electrically couple adjacent modules sothat power and/or communication signals can be passed between modules.The near connector of PCBA 911 is not used because module 910 is theunit on the farthest right of the system 900. The far connector of PCBA911 is coupled through an electric cable, e.g. a flat cable, to the nearconnector of PCBA 921. Similarly, the far connector of PCBA 921 iscoupled through an electric cable to the near connector of PCBA 931, andthe far connector of PCBA 931 is coupled through an electric cable tothe near connector of PCBA 941. The far connector of PCBA 941 is notused because module 940 is the unit on the farthest left of the system900.

The cables plug into the near connector of the PCBA through a window,and the windows can be covered with a plate. This setup allows eachlight module 910, 920, 930, 940 to slide into place, for example, asceiling units. Because the emission surface of each light pipeseamlessly contacts the neighboring light pipe, there is no room toelectrically couple the units using integrating sockets or any othermethod that would require a sideways movement of the module.

The electric cables can include a first cable that is used to transmitcommunication signals between the light modules 910, 920, 930, 940. Inone embodiment, one of the light modules is a master unit, for example,primary module 910. Only primary module 910 receives commands from anexternal source, for example, either wirelessly through a radio receiveror through wired means. The commands can include, but are not limitedto, tuning the color temperature of the light emitted by all of themodules, adjusting the intensity of the illumination, calibrating thelight modules, and turning the modules on or off. Primary module 910then re-transmits the commands to the rest of the modules 920, 930, 940in the system 900 through the electric cables. Because the other modules920, 930, 940 do not have a radio receiver or a wired signal receiver,the cost of the system is reduced.

In one embodiment, each of the modules 910, 920, 930, 940 of the system900 has a wired or wireless receiver to receive commands from anexternal source. Then the primary module 910 or any other module 920,930, 940 can re-broadcast the commands to the other modules through theelectric cables. In this case, the communications through the flatcables act as a redundant communication system. If a module has alreadyreceived the command from the external source, it can ignore there-broadcast command.

The electric cables can also include a second cable that is used totransmit power between the light modules 910, 920, 930, 940. In oneembodiment, the primary module 910 can include a power supply largeenough to provide power to the other three modules 920, 930, 940.Depending on the strength of the power supply, a single module canprovide power through the electric cables to even more modules.Alternatively, multiple power supplies can be used within the system,depending upon how many modules need power.

FIG. 14 includes a master printed circuit board assembly (PCBA) 1452 anda slave PCBA 1454 on opposite ends of a composite linear light module1400 that includes two individual linear light modules coupled together.In one example, the master PCBA 1452 is electrically coupled to theslave PCBA 1454. Both the PCBA 1452 and the PCBA 1454 are printedcircuit boards or other forms of embedded circuitry. The master PCBA1452 includes a master controller module, such as a microprocessor, aradio communication device, and a memory module.

The master PCBA 1452 includes a first optical sensor 1456 to provideoptical feedback during calibration. The slave PCBA 1454 also includes asecond optical sensor 1458 for feedback to the master PCBA 1452. Thefirst optical sensor 1456 and the second optical sensor 1458 can bebroad spectrum optical sensors, such as PIN diodes. The PIN diodes arediodes with wide, lightly doped near intrinsic semiconductor regionbetween of a p-type semiconductor and an n-type semiconductor region.One example of a suitable PIN diode that can be used is the PD15-22C/TR8PIN diode manufactured by Everlight Electronics Co., Ltd. Of New TaipeiCity, Taiwan. Both the master PCBA 1452 and the slave PCBA 1454 caninclude one or more thermal sensors near the LED array, such as thethermistor 1350 of FIG. 13A. The thermistor changes resistance based ontemperature of its environment.

The PIN diodes 1456, 1458 are oriented on the back side of the printedcircuit board assemblies seen in FIG. 14, facing toward a side surfaceof the light pipe. As described above, the side surfaces of each lightpipe are backed by a reflective surface. Consequently, a hole is formedin the reflective surface near each PIN diode to allow a small portionof light to escape to be sensed by the PIN diode.

The master PCBA 1452 includes circuitry to perform self calibration onthe fly. The slave PCBA 1454 can also perform self calibrationon-the-fly. Self calibration can be performed via optical feedbackthrough the optical sensor 1456. The LEDs degrade over time. Some colorLED degrades more so than others. For example, the red LEDs degrade mostwith life and the blue LEDs are most resistant to degradation. Hence,during the self calibration the red color over blue color ratio ismeasured and compare with factory values. Then the blue LED current islower to reset the present color ratio to that of the factory setting asthe red color LEDs degrade.

FIG. 16 illustrates an example block diagram of a master PCBA 1602coupled with a slave PCBA 1604. The master PCBA 1602 can be the masterPCBA 1452 of FIG. 14. The slave PCBA 1604 can be the slave PCBA 1454 ofFIG. 14. The master PCBA 1602 includes a power connection 1606 and a LEDdriver 1608. The power connection 1606 provides electrical power to theLED driver 1608 to drive a first plurality of LEDs 1609. The LED driver1608 can be configured by a master controller module 1610. The mastercontroller module 1610 is electrical circuitry for configuring the LEDdriver 1608. The master controller module 1610 can be a microprocessoror other controller type embedded within the master PCBA 1602. Commandscan be sent to the master controller module 1610 from an external userinterface 1601, such as dimming the intensity of the light with the sameCCT or changing the CCT of the light. Further, the mater controllermodule 1610 can perform algorithms for tuning the CCT of the LEDs suchas described in U.S. patent application Ser. No. 13/766,695 entitled,“System and Method for Color Tuning Light Output from an LED-BasedLamp.”

Communications between the external user interface 1601 and the mastercontroller module 1610 can be via RS-232 or RS-485 standards, forexample. Similarly, communications between the master controller module1610 and the slave controller 1628 can also be via RS-232 or RS-485standards, for example.

The master controller module 1610 can receive inputs from an opticalsensor module 1612. The optical sensor module 1612 can be a pin diode,such as the pin diodes illustrated in FIG. 14, coupled to electroniccircuitry to transmit a sensed color spectrum to the master controllermodule 1610. The master controller module 1610 can also receive inputsfrom a thermal sensor module 1614. The thermal sensor module 1614 canreceive temperature information from a thermistor, such as thethermistor 1350 of FIG. 13A, on the master PCBA 1602 or adjacent to thefirst plurality of LEDs 1609. The sensory information received can bestored on a memory module 1616 of the master PCBA 1602. The sensoryinformation can be stored as a sensor history database 1618. Whenconfiguring the LED driver 1608, the master controller module 1610 canrefer to a color model 1620 stored on the memory module 1616. The colormodel 1620 provides a driving signal to produce a particular colorspectrum based on an operating temperature and a driving current level.The thermal sensor 1614 can provide the operating temperature.

The first plurality of LEDs 1609 may degrade over time. Some color setsdegrade more so than others. For example, a red color set within thefirst plurality of LEDs 1609 may degrade faster than a blue color set.The master controller module 1610 is configured to calibrate the firstplurality of LEDs 1609. In one example, the master controller module1610 can calibrate the first plurality of LEDs 1609 to return to itsfactory settings. A factory setting database 1622 can be stored on thememory 1616. The factory setting database 1622 may store ratios ofcolors, such as a red color intensity over a blue color intensity or anamber color intensity over a blue color intensity. The optical sensormodule 1614 can provide color spectrum information to the mastercontroller module 1610 in order to return the present color ratios tothe factory setting as according to the factory setting database 1622.

In some embodiments, to determine the present color ratios, the mastercontroller module 1610 can flash each color set of the first pluralityof LEDs 1609 and measure the intensity of the color sensed by theoptical sensor module 1614. The measured color intensities of differentcolors can be normalized against a chosen color set, such as blue LEDs,to arrive at the present color ratios of the first plurality of LEDs1609. The master controller module 1610 can lower a driving current fora blue color set of LEDs amongst the first plurality of LEDs 1609 untilthe present color ratio with respect to the blue color is the same asthe factory setting ratio in the factory setting database 1622.

The master PCBA 1602 can also include a radio module 1624 to communicatewith an external control device, such as a remote control. The radiomodule 1624 may be a radio transceiver or a set of a radio transmitterand radio receiver. The radio module 1624 can receive commands, such ascalibration commands or commands to match a particular color spectrum ora particular correlated color temperature (CCT). The radio module 1624can also transmit the current sensor information, the color model 1620,the sensor history 1618, the factory setting database 1622, or anycombination thereof.

The master PCBA 1602 further includes a slave interface 1626 forcommunicating with the slave PCBA 1604. The slave PCBA 1604 includes amaster interface 1628 for communicating with the master PCBA 1602. Themaster interface 1628 receives configuration messages from the slaveinterface 1626 of the master PCBA 1602. The configuration messagesdictate how a LED driver 1630 of the slave PCBA 1604 drives the secondplurality of LEDs 1631. The LED driver 1630 derives its power from apower connection 1632. The configuration received via the configurationmessages can be stored in a memory module 1634 of the slave PCBA 1604.

The slave PCBA 1604 can also include a slave thermal sensor module 1636and a slave optical sensor module 1638 for providing thermal and opticalfeedback through the master interface 1628, such that the mastercontroller module 1610 can determine the driving signal configurationfor the LED driver 1630 of the slave PCBA 1604. The master controllermodule 1610 can determine the driving signal configuration for the LEDdriver 1630 the same way it determines the driving signal configurationfor the LED driver 1609, such as through calibration.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense (i.e., to say, in thesense of “including, but not limited to”), as opposed to an exclusive orexhaustive sense. As used herein, the terms “connected,” “coupled,” orany variant thereof means any connection or coupling, either direct orindirect, between two or more elements. Such a coupling or connectionbetween the elements can be physical, logical, or a combination thereof.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, refer to this application as awhole and not to any particular portions of this application. Where thecontext permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or,” in reference to a list of two or moreitems, covers all of the following interpretations of the word: any ofthe items in the list, all of the items in the list, and any combinationof the items in the list.

The above Detailed Description of examples of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific examples for the invention are describedabove for illustrative purposes, various equivalent modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize. While processes or blocks are presented ina given order in this application, alternative implementations mayperform routines having steps performed in a different order, or employsystems having blocks in a different order. Some processes or blocks maybe deleted, moved, added, subdivided, combined, and/or modified toprovide alternative or subcombinations. Also, while processes or blocksare at times shown as being performed in series, these processes orblocks may instead be performed or implemented in parallel, or may beperformed at different times. Further any specific numbers noted hereinare only examples. It is understood that alternative implementations mayemploy differing values or ranges.

The various illustrations and teachings provided herein can also beapplied to systems other than the system described above. The elementsand acts of the various examples described above can be combined toprovide further implementations of the invention.

Any patents and applications and other references noted above, includingany that may be listed in accompanying filing papers, are incorporatedherein by reference. Aspects of the invention can be modified, ifnecessary, to employ the systems, functions, and concepts included insuch references to provide further implementations of the invention.

These and other changes can be made to the invention in light of theabove Detailed Description. While the above description describescertain examples of the invention, and describes the best modecontemplated, no matter how detailed the above appears in text, theinvention can be practiced in many ways. Details of the system may varyconsiderably in its specific implementation, while still beingencompassed by the invention disclosed herein. As noted above,particular terminology used when describing certain features or aspectsof the invention should not be taken to imply that the terminology isbeing redefined herein to be restricted to any specific characteristics,features, or aspects of the invention with which that terminology isassociated. In general, the terms used in the following claims shouldnot be construed to limit the invention to the specific examplesdisclosed in the specification, unless the above Detailed Descriptionsection explicitly defines such terms. Accordingly, the actual scope ofthe invention encompasses not only the disclosed examples, but also allequivalent ways of practicing or implementing the invention under theclaims.

While certain aspects of the invention are presented below in certainclaim forms, the applicant contemplates the various aspects of theinvention in any number of claim forms. For example, while only oneaspect of the invention is recited as a means-plus-function claim under35 U.S.C. §112, sixth paragraph, other aspects may likewise be embodiedas a means-plus-function claim, or in other forms, such as beingembodied in a computer-readable medium. (Any claims intended to betreated under 35U.S.C. §112, ¶ 6 will begin with the words “means for.”)Accordingly, the applicant reserves the right to add additional claimsafter filing the application to pursue such additional claim forms forother aspects of the invention.

1. An optical element comprising: a light transmissible body; an inputsurface of the light transmissible body configured to receive lightemitted by a plurality of light emitting elements; a plurality ofintermediate surfaces of the light transmissible body configured tocouple the input surface to an output surface of the light transmissiblebody, wherein the plurality of intermediate surfaces are configured toreflect a substantial amount of the received light through totalinternal reflection (TIR) within the light transmissible body to exitthe light transmissible body through an output surface opposite theinput surface, and further wherein light exiting the output surfacemeets an exit angle criteria such that the exiting light is within apredefined range of exit angles with respect to a normal to the outputsurface; the output surface of the light transmissible body isconfigured to meet a predefined aperture criteria.
 2. The opticalelement of claim 1, wherein the optical element is symmetric along twoaxes, wherein the two axes are perpendicular to a direction normal tothe output surface.
 3. The optical element of claim 1, wherein one ormore of the plurality of intermediate surfaces have a substantiallyparaboloid curvature.
 4. The optical element of claim 1, wherein thelight emitting elements are light emitting diodes, and further whereinthe input surface includes one or more concave inward cavities.
 5. Theoptical element of claim 4, wherein the one or more concave inwardcavities each receive a single light emitting diode, and further whereina coupling material is used between the light emitting diodes and theone or more cavities.
 6. The optical element of claim 4, wherein the oneor more concave inward cavities each receive a plurality of lightemitting diodes, and further wherein a coupling material is used betweenthe light emitting diodes and the one or more cavities.
 7. The opticalelement of claim 1, further comprising a plurality of reflectivesurfaces positioned adjacent to the plurality of intermediate surfacesto reflect light that exits the light transmissible body through atleast one of the plurality of intermediate surfaces back into the lighttransmissible body, wherein an air gap is between the plurality ofreflective surfaces and the plurality of intermediate surfaces.
 8. Theoptical element of claim 1, wherein the predefined range of exit anglesis specified so that the exiting light is substantially totallyinternally reflected within a light guide directly coupled to the outputsurface until the light is emitted along an emission surface of thelight guide substantially perpendicular to the output surface of theoptical element.
 9. The optical element of claim 8, wherein the lightguide extends substantially perpendicular to the output surface and hasa substantially rectangular solid shape.
 10. The optical element ofclaim 8, wherein the light guide extends substantially perpendicular tothe output surface and has a bottom surface opposite the emissionsurface that is tapered toward the output surface.
 11. The opticalelement of claim 8, wherein the light guide extends substantiallyperpendicular to the output surface and has a bottom surface oppositethe emission surface that is a step surface that rises toward the outputsurface.
 12. The optical element of claim 8, wherein a scatteringelement is positioned beneath at least a portion of a bottom surface ofthe light guide opposite the emission surface, wherein an air gap isbetween the scattering element and the bottom surface.
 13. The opticalelement of claim 1, wherein a light extraction element is coupled to atleast one of the intermediate surfaces to cause light to fail to meet aTIR condition and to exit from the optical element at the lightextraction element.
 14. A light guide comprising: a light transmissiblebody; an input surface of the light transmissible body configured toreceive light from an optical coupling element configured to couplelight from a plurality of light emitting elements, wherein a substantialamount of the received light is within a range of angles that is totallyinternally reflected upon striking an inner surface of the lighttransmissible body; an emission surface of the light transmissible bodyconfigured to emit light that strikes the emission surface and does notmeet a total internal reflection (TIR) condition, wherein the emissionsurface has a linear configuration, is substantially perpendicular tothe input surface, and is cantilevered over the optical couplingelement; a plurality of side surfaces of the light transmissible bodyconfigured to reflect light within the light transmissible body by TIRif the light meets the TIR condition; a plurality of reflective surfacesadjacent to at least some of the plurality of side surfaces, separatedby an air gap from the at least some of the plurality of side surfaces,and configured to reflect light that exits the at least some of theplurality of side surfaces.
 15. The light guide of claim 14, wherein abottom surface opposite the emission surface has an undulating curvatureto scatter the received light.
 16. The light guide of claim 14, whereinone or more scattering elements are positioned adjacent to at least aportion of a bottom surface of the light guide opposite the emissionsurface, and wherein an air gap is between the one or more scatteringelements and the bottom surface.
 17. The light guide of claim 16,wherein the one or more scattering elements comprise a brightnessenhancement film.
 18. The light guide of claim 17, wherein the one ormore scattering elements are angled at two or more orientations.
 19. Thelight guide of claim 16, wherein the one or more scattering elements area diffusive material covering the entire bottom surface.
 20. The lightguide of claim 16, wherein the one or more scattering elements are adiffusive material covering at least a portion of the bottom surface ina uniform pattern.
 21. The light guide of claim 16, wherein the one ormore scattering elements are a diffusive material covering at least aportion of the bottom surface in a non-uniform pattern.
 22. The lightguide of claim 16, wherein the bottom surface is substantially parallelto the emission surface.
 23. The light guide of claim 16, wherein thebottom surface is tapered toward the emission surface.
 24. The lightguide of claim 16, wherein the bottom surface is a step surface thatrises toward the output surface.
 25. The light guide of claim 14,wherein a bottom surface opposite the emission surface curves upward.26. The light guide of claim 25, wherein the bottom surface hassaw-tooth features.
 27. The light guide of claim 26, wherein thesaw-tooth features vary in amplitude.
 28. The light guide of claim 27,wherein an amplitude of each of the saw-tooth features decreasesmonotonically from a close end of the emission surface near the opticalcoupling element to a far end of the emission surface.
 29. The lightguide of claim 14, further comprising a diffuser between the inputsurface of the light transmissible body and the optical couplingelement.
 30. The light guide of claim 14, wherein a bridge portion ofthe light transmissible body cantilevered over the optical couplingelement is separated from the optical coupling element by an air gap,and the light guide further comprises a light extraction element coupledto a top surface of the optical coupling element closest to the bridgeportion of the light transmissible body.
 31. The light guide of claim14, wherein the plurality of light emitting elements comprise aplurality of light emitting diodes (LEDs) arranged in an array, whereinthe plurality of LEDs are selected to emit a plurality of colors tocollectively generate a particular correlated color temperature (CCT),and further wherein a relative placement of LEDs within the array isbased on a position of each of the plurality of colors on a CIE(International Commission on Illumination) color diagram.
 32. The lightguide of claim 31, wherein the array comprises rows of pairs of LEDs,and further wherein each pair of LED is selected to comprise a first LEDlocated across a Planckian curve on the CIE color diagram from a secondLED.
 33. A lighting system comprised of two light guides of claim 14,wherein the emission surface of the two light guides are aligned to forma straight composite emission surface, and further wherein the opticalcoupling element of each light guide is positioned near the ends of thelight system.
 34. The lighting system of claim 33, further comprising anoutput reflector, wherein the output of the emission surface isreflected from the output reflector.
 35. The lighting system of claim33, further comprising an output diffuser, wherein the output of theemission surface is transmitted through the output diffuser.